UWB (Ultra Wide Band) refers to short-distance wireless communication techniques that are being developed in recent years. The UWB technology for the microwave band has been standardized by WiMedia, which is an industry organization of UWB, and products (for example, wireless USB's) conforming to the UWB technology will be released in near future.
The multiaccess technology is introduced in wireless communication of comparatively short distance communication such as UWB and Wi-Fi (Wireless Fidelity) in terms of necessity to effectively utilize bands. Wi-Fi realizes multiaccess by means of exclusive control based on a carrier detecting function according to CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) which is a wireless version of the CSMA/CD (Carrier Sense Multiple Access with Collision Detection) protocol of Ethernet (registered trademark). Characteristics of Wi-Fi include employing a star formed network that mediates access points. Further, Non-Patent Document 1 discloses the Wi-Fi technique.
Further, WiMedia realizes multiaccess by means of slot reservation type exclusive control based primarily on TDMA (Time Division Multiple Access). Furthermore, the network form according to Wi-Media is a mesh type that configures the network in which each node transmits a beacon from one another.
Specific characteristics of radio waves in the millimeter wave band include directivity. That is, radio waves in the millimeter wave band have directivity, which is different from radio waves in the micro wave band. There is a demand that multiaccess is realized in wireless communication schemes using UWB for the millimeter wave band, that is, wireless communication schemes using directional radio waves.
The transmission distance in UWB is extremely short, and, therefore, a UWB application is, for example, WPAN (Wireless Personal Area Network). PAN is a network technique for connecting, in the wide band, devices owned by individuals, and WPAN is assumed to connect digital household appliances by radio. Non-Patent Document 2 discloses the current configuration of MAC (Medium Access Control) in WPAN.
Non-Patent Document 1: “Local and metropolitan area networks—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” ANS/IEEE Standard 802.11, 1999 Edition
Non-Patent Document 2: “Local and metropolitan area networks—Part 15.3: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for High Rate Wireless Personal Area Networks (WPAN's),” IEEE Standard 802.15.3-2003